In ventilation duct systems, sealing gaskets are oftentimes used to provide a generally air-tight seal at the joints of the various ventilation duct components. In known sealing systems, an elastic sealing gasket or ring, typically made of rubber, is positioned in a groove about one or both connection ends of a fitting, and the fitting is then inserted into receiving ends of the duct runs for connecting and branching the ventilation duct system. The sealing gasket has one or more sealing flanges that extend radially outwardly from the connection end of the fitting and engage the inside surface of the receiving end of a duct run into which the fitting is inserted to form a seal.
One example of a known sealing gasket used in ventilation duct systems comprises a double-lip seal having a U-shaped cross-section. The sealing gasket is anchored in a circumferential groove formed in one or both ends of the fitting. The sealing gasket has a central web that is applied against the outside surface of the fitting and is fastened by a clamping ring that is placed onto the web of the sealing gasket and then tightened. The clamping ring is then anchored by spot welding. The sealing gasket has two sealing flanges that project radially outwardly on opposite sides of the clamping ring. The sealing flanges are bent sideways when the fitting is inserted into the end of the duct run so that a sealing effect is achieved by engagement of the sealing lips with the inside surface of the duct run end. Fasteners, such as screws, are driven through the receiving ends of the duct runs and the connection ends of the fittings to secure the components together.
While the double-lip seal described above provides an effective seal at the joints of the ventilation duct system, this sealing system is oftentimes difficult and labor intensive to install on the ends of the fittings and requires multiple parts to form and anchor the sealing gasket to the fitting which increases cost.
Another problem oftentimes encountered in known ventilation ducts systems is leakage of air at the locations of the fasteners which then escapes from the joints. While the fasteners typically include washers or gaskets so as to form an air-tight seal at the holes formed though the outer ends of the duct runs, the holes formed through the inner connection ends of the fitting are susceptible to air leakage. Air leaking through these holes migrates through the annular gap formed between the components and then escapes from the joint. Thus, while the sealing gaskets provide a generally air-tight seal at the joints of the ventilation duct components, the sealing gaskets are not positioned to provide any sealing effect to minimize or eliminate air leakage from the joints caused by the fastener holes.
Thus, there is a need for an improved sealing gasket that overcomes these and other shortcomings and drawbacks of known sealing gaskets for use in ventilation duct systems.